Stabilized unit train

ABSTRACT

A UNIT RAILROAD TRAIN HAVING A SERIES OF LIKE CARS, THE TRAIN BEING SUBJECT TO RESONANCE EFFECTS WHICH MAKE IT DIFFICULT FOR THE TRAIN TO ATTAIN OPTIMUM SPEED. TO OVERCOME THIS DRAWBACK, TWO OR MORE CARS IN THE SERIES THEREOF AT SEPARATED POINTS THEREIN ARE PROVIDED WITH STABILIZERS WHICH TAKE THE FORM OF LIQUID STORAGE TANKS WHEREIN LIQUID IS TRANSFERRED FROM ONE SECTION OF THE TANK TO ANOTHER IN A DIRECTION TRANSVERSE TO THE MOVEMENT OF THE TRAIN, THE RHYTHM OF LIQUID TRANSFER BEING OUT OF PHASE WITH THE UNDULATION OF UNIT TRAIN AT ITS NATURAL PERIOD OF VIBRATION, THEREBY INTERRUPTING THIS PERIOD AND MAKING IT POSSIBLE FOR THE TRAIN TO REACH HIGHER SPEEDS WITHOUT RESONANCE EFFECTS.

Sept. 20, 1971 w. R. TOWNSEND STABILIZEDUNIT TRAIN Filed March 25, 1969 INVIL'N'IHR MLUAM R 75w-swo United States Patent 3,605,633 STABILIZED UNIT TRAIN William R. Townsend, Old Greenwich, Conn., assignor to Flume Stabilization Systems, Inc., Hoboken, NJ. Filed Mar. 25, 1969, Ser. No. 810,221 Int. Cl. B61d /00 U.S. Cl. 1051 8 Claims ABSTRACT OF THE DISCLOSURE A unit railroad train having a series of like cars, the train being subject to resonance effects which make it difficult for the train to attain optimum speed. To overcome this drawback, two or more cars in the series thereof at separated points therein are provided with stabilizers which take the form of liquid storage tanks wherein liquid is transferred from one section of the tank to another in a direction transverse to the movement of the train, the rhythm of liquid transfer being out of phase with the undulation of the unit train at its natural period of vibration, thereby interrupting this period and making it possible for the train to reach higher speeds without resonance effects.

BACKGROUND OF THE INVENTION This invention relates generally to the stabilization of railroad trains and more particularly to a passive stabilization system adapted to minimize resonance effects in unit trains, thereby making it possible for such trains to operate more efficiently and to attain their optimum speed.

A unit train is one made up of a series of like cars which are intercoupled, such as flat cars, tank cars, box cars or gondolas. A unit train is useful in transporting loads of coal, ore, grain or oil from a single source to a common destination. Hence in unit train operations, there is no need for marshalling areas to assemble cars of different types or for interchange operations to break up and reassemble trains to direct various cars toward different routes. Because operating costs are much lower, unit trains enjoy reduced tariffs.

By reason of their homogeneous nature, unit trains would appear to lend themselves to high speed operations, particularly over straight line, long haul routes in the plains states where track conditions are almost ideal for this purpose. But experience has shown that unit trains are subject to disturbing resonance effects which preclude travel at optimum speeds.

An interconnected series of identical cars carrying a similar cargo behaves to some degree like a unitary string or reed having a natural period of harmonic motion which depends on its overall length. In movement over the rails, each car in a unit train will undergo individual motions, such as rocking, swaying and rolling. However, when the unit train attains a certain speed, it is excited into resonance at the natural period of the entire system. This vibration takes the form of undulations of high amplitude which involve all of the cars forming the unit and override the individual motions of the cars; the period of the undulations being a function of the train length and other factors.

These unit train undulations create a hazardous condition and it is necessary therefore, in the interest of safety, that the unit train be run well below the speed at which resonance effects are encountered. Hence with ordinary unit trains it is not possible to attain optimum speeds.

The phenomenon of structural resonance is not only encountered in unit trains, for in the context of bridges it is known that should troops being marched in unison thereacross, the bridge may be set into rhythmic vibration at its resonance frequency with destructive results. It is for this reason that troops are ordered to break step when crossing a bridge.

In order to overcome resonance effects in unit trains and to break up the undulatory period, it has heretofore been the practice to introduce disparate types of cars in the chain of cars constituting the train. Thus by interspersing flat cars at different points in a train otherwise made up of box cars, one may reduce or eliminate resonance effects. But in doing so, a mixed train rather than a unit train is produced and the distinct advantages of unit train operations are lost.

SUMMARY OF INVENTION In view of the foregoing, it is the main object of this invention to provide a unit train composed of like cars, which train is substantially free of resonance effects and is capable of attaining optimum speed.

More particularly, it is an object of this invention to provide a passive stabilization system for unit trains, which system acts to break up the natural undulatory period thereof and to prevent resonance effects at high speed operation.

Also an object of the invention is to provide a system of the above type which is relatively inexpensive to construct, to install and to operate.

Briefly stated, these objects are attained in a unit train composed of a series of like cars, some of the cars in the series at separated points therein having a passive stabilizer in the form of a liquid storage tank which is adapted to permit the free flow of liquid from one section of the tank to another section thereof in a direction transverse to the movement of the car, the rhythm of liquid transfer from one tank section to the other being out of phase with the undulation of the train at its resonance frequency, thereby damping the undulation to produce a stabilizing effect.

It is important to note that the stabilizer tank is tuned to operate not with respect to the roll or sway of the individual car in which it is installed, but in reference to the overall natural period of the unit train in order to interrupt this period, the stabilizers acting as discontinuities in the chain of cars.

BRIEF DESCRIPTION OF THE DRAWINGS For a better understanding of the invention, as well as other objects and further features thereof, reference is made to the following detailed description to be 'read in conjunction with the annexed drawing, wherein:

FIG. 1 schematically shows a unit train composed of box cars, some of which includes passive stabilizers in accordance with the invention;

FIG. 2 is a longitudinal section taken partially through one of the box cars including the stabilizer;

FIG. 3 is a cross-section taken in the plane indicated by lines 33 in FIG. 2;

FIG. 4 illustrates a stabilizer for use with a containerized unit train.

DESCRIPTION OF THE INVENTION Referring now to FIG. 1, there is shown a unit train running along a trackway 10 and composed of an engine 12 coupled to a series of like cars 11A, 11B, 110, etc. By way of example, the cars are shown as box cars, but it will be appreciated that other standard types of cars may be used to form the unit train.

A series of like cars, such as cars 11A, 11B, 110, etc., form an unbroken chain or string whose length depends, of course, on the number of cars in the series. As the cars travel over the rails, which may be uneven or irregular, each car undergoes various motions such as swaying, roll- 3 ing and jogging. But such movement, as long as track conditions are good and the movement is not excessive, will not prevent a unit train from traveling at high speed.

The factor which does create serious difiiculty is the resonance characteristic of the series, pointed out previously, for at a particular speed, a unit train will be excited into undulation at a period which depends on the length of the train and other factors, and which causes the cars to sway to a dangerous degree even on a straight trackway.

To break up the undulatory period, two or more of the cars at separated points in the series forming the unit are provided with passive stabilizers in accordance with the invention. Thus in a series composed of cars 11A to 11Z, the cars 11B, 11F, 11], UN and 11V may have stabilizers installed therein, not for the purpose of dampening motion of these cars at their individual motion frequencies, but of impeding the overall undulation of the unit train at its natural period.

In effect, therefore, these stabilizers function as discontinuities or isolation stages in the unit chain and prevent the train from being excited into resonance. Preferably, the stabilizers are located at discrete points which effectively break the string series into uneven pieces incapable of resonating in the same period.

FIGS. 2 and 3 show one of the box cars (B) which incorporate stabilizers. At opposite ends of this car there are installed stabilizers, generally designated as S and S These stabilizers are of the type heretofore used in oceangoing vessels and disclosed for example in the patents;

In one simple form of such stabilizer, an elongated tank is mounted transversely with respect to the hull of the vessel, energy damping means being disposed at the center line of the tank to divide it into two intercommunicating compartments. The stabilizer is characterized by the fact that a body of water within the tank tends to assume a free surface condition throughout the tank and by the fact that there is cooperation between the two compartments for creating a restoring moment in response to the roll of the ship.

In operation, the rhythm of liquid transfer from one tank compartment to the other is approximately 90 out of phase, leading the rolling angle when the vessel is rolling at resonance, thereby producing a stabilizing effect to minimize such rolling. This type of stabilizer takes various other forms and may be constituted for example by two distinct tanks interconnected by a flume or a single tank divided into three or more compartments 1 sections by restricted openings or damping means. In all instances, stabilization depends on the rhythmic transfer of liquid out of phase to the vessel motion which gives rise to the transfer.

The stabilizers S and S shown in FIGS. 2 and 3 are each constituted by a tank 13 which extends across the car and is partially filled with a liquid 14, Which may be water or oil, the static level of which is indicated at 15. Each tank includes damping members or baflles 16 and 17 depending vertically from the top 18 of the car, the lower end of the baflie being spaced from the floor 19 of the tank, thereby defining two end compartments 20 and 21 and an intermediate compartment 22 which communicates with each other through bottom openings. Baffles 16 and 17 are provided with air holes 23 and 24 respectively.

The liquid passing from tank compartment 20 on one side of the car to the compartment 21 on the other side thereof goes through the lower openings or nozzles 25 and 26 formed by the baffles, which nozzles retard the free flow of liquid. The air holes serve to prevent pressure build-up so as not to impede the flow of liquid across the compartments. In practice, the bottom level of the 4 tank may be raised relative to the bottom of the car to elevate the static liquid level above the center of roll, thereby adding to the effective moment created by the stabilizing tank.

The tuning of stabilizers S and S depends on the r lative horizontal and vertical cross-sectional dimensions of the tanks, the viscosity of the liquid and other parameters which are set forth in detail in the above-identified patents. The stabilizers are tuned to provide a rhythm of liquid transfer in a direction transverse to the travel direction out of phase with the undulations at the resonance frequency of the entire unit train. In tuning one does not take into account the roll of the car in which the stabilizer is installed. Thus the stabilizer functions to break the period of these unit train undulations and only incidentally to some degree to dampen the individual roll of the car in question.

In other words, the stabilizer is tuned to be operative as a dampening agent only when the speed of the unit train is likely to set the entire train into undulation at its natural period, the tuning being unrelated to the roll frequency of the car.

It is not essential to permanently incorporate the stabilizer in the car and in practice the stabilizer may be a separate box which is attachable to appropriate cars. Thus as shown in FIG. 4, the unit train may be made up of flat cars carrying standardized cargo containers 27, 28, 29 and 30 of the type used in integrated transportation system for ready transfer from trucks to trains to containerships. Such containers are provided with top and bottom corner fittings 27A and 2713, 28A and 28B, 29A and 29B, and 30B to facilitate lifting, stacking, anchoring and other handling operations.

By providing self-sufficient stabilizer tanks 5;, and S having fixtures adapted to be coupled to the corner fittings of the containers one may attach these stabilizers to appropriate containers on the unit train to obtain the desired stabilizing effect. Stabilizers may be mounted atop the containers or at the end of a group thereof on a flat car, whichever arrangement is appropriate. In practice, the tanks may be provided with valves to adjust the liquid level and thereby permit tuning of the tanks.

In some instances, depending on train length and other factors, the frequency of roll of individual cars containing stabilizers, may be close to the natural period of the entire train, in which even the stabilizers would also serve to dampen the individual roll. While it is only necessary to introduce stabilizers at separated points in the train, in practice, all of the cars may be equipped with stabilizer tanks, with selected ones being filled with liquid and being tuned as required.

In the embodiment of the invention illustrated in FIGS. 2 and 3, box cars are given as an example of like cars in a unit train. Actually, such cars will behave as like cars only if similarly loaded, which in practice may not be the case when the cargo in the various cars is diversified. But where bulk cargoes, such as coal, are carried in gondolas or other cars appropriate to bulk loads, the cars in the train then have characteristics which are virtuaily identical, and hence the train is more likely to resonate at a natural period.

What I claim is:

1. A unit train comprising a series of similar cars, similarly loaded and being subject to resonance effects when the train attains a particular high speed, said resonance effects causing the unit train to undulate at a natural period which is a function of train length, which is unrelated to the individual motions of the cars, and which involves all of the cars forming the train; a system for preventing said unit train from undulating at the natural period, said system comprising stabilizers disposed at predetermined spaced intervals along the length of said unit train; each stabilizer being constituted by at least one tank in which liquid is rhythmically transferable from one section thereof to another in a direction transverse to the movement of the train through damping means and at a rate which is out of phase with said natural period for purposes of damping said resonance effects.

2. A system as set forth in claim 1, wherein said cars are box cars, and wherein those box cars having stabilizers are provided with one of said tanks at either end of the car.

3. A system as set forth in claim 1, wherein said cars are all gondolas.

4. A system as set forth in claim 1, wherein each tank car includes baflies dividing the tank into compartments which intercommunicates through nozzles.

5. A system as set forth in claim 4, wherein said baffles include air holes above the liquid level.

6. A system as set forth in claim 1, wherein said stabilizers are at separated points in said series which break the series into uneven sections.

7. A system as set forth in claim 1, wherein said cars are fiat cars for carrying standard cargo containers provided with corner fittings, and said tanks have fixtures to couple said tanks to said containers.

8. A system as set forth in claim 1, wherein said tank is provided with valves to adjust the liquid level therein to tune the stabilizer.

References Cited DRAYTON E. HOFFMAN, Primary Examiner US. Cl. X.R. 105-238 

